New closure instances of functions like parse-loop get l_compiled=None
even though a previous instance already failed. Now check _jit_warned
by name and immediately sentinel-mark new instances of known failures.
The first failure is always logged. Subsequent instances are silently
sentinel-marked — no recompilation, no log spam, no suppressed errors.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>